This invention relates to an electron beam exposure apparatus, more specifically to an exposure apparatus capable of adjusting at need the exposure to an electron beam.
In exposing a subject material, e.g. photo-resist material by means of an electron beam exposure apparatus, it is necessary to adjust suitably the amount of electron beam applied to the photo-resist material according to the conditions thereof, such as pattern shape and thickness so as to overcome a proximity effect.
As means for adjusting the exposure to the electron beam, there are conventionally known the following systems.
(1) Means for changing the magnification of a condenser lens.
(2) Means for changing the grid bias voltage of an electron beam generator.
(3) Means for changing the drawing (exposure) speed.
According to the first means, the diameter, advancing path and converging position of the electron beam on the subject material will vary if the magnification of the condenser lens is changed. In addition, the magnification of the condenser lens cannot be changed in a short time.
According to the second means, the diameter and beam position of the electron beam will vary in the same manner as the case of the first means, and the capacity of an electron gun is large, failing to make a high-speed change in the voltage.
As for the third means, it cannot be applied to the random scanning system in which the drawing speed is preset, though a satisfactory result may be obtained with the vector scanning system. After all, in the prior art apparatuses employing these systems, it has been very difficult to ensure high-accuracy exposure to electron beam because the amount of electron beam applied has not been able to be adjusted effectively.